Control strategy for reducing boom oscillation

ABSTRACT

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic cylinder (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and first and second blocking valves (350, 450). A net load (90) is supported by a first chamber (116, 118) of the hydraulic cylinder, and a second chamber (118, 116) of the hydraulic cylinder may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The method may include measuring first pressure ripples at the second chamber and reducing a magnitude of second pressure ripples at the first chamber. The pressure ripples may be transformed into a flow command by multiplying the pressure ripples by a gain and/or phase shifting. The gain and/or the phase shifting may be adjusted by feedback. The feedback may include the second pressure ripples at the load holding chamber, a position of the hydraulic actuator, and/or an operator input. A reference signal may be filtered with a moving average filter.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a National Stage of PCT/US2014/064651, filed on Nov.7, 2014, which claims benefit of U.S. Patent Application Ser. No.61/904,340 filed on Nov. 14, 2013 and which applications areincorporated herein by reference. To the extent appropriate, a claim ofpriority is made to each of the above disclosed applications.

BACKGROUND

Various off-road and on-road vehicles include booms. For example,certain concrete pump trucks include a boom configured to support apassage through which concrete is pumped from a base of the concretepump truck to a location at a construction site where the concrete isneeded. Such booms may be long and slender to facilitate pumping theconcrete a substantial distance away from the concrete pump truck. Inaddition, such booms may be relatively heavy. The combination of thesubstantial length and mass properties of the boom may lead to the boomexhibiting undesirable dynamic behavior. In certain booms in certainconfigurations, a natural frequency of the boom may be about 0.3 Hertz(i.e., 3.3 seconds per cycle). In certain booms in certainconfigurations, the natural frequency of the boom may be less than about1 Hertz (i.e., 1 second per cycle). In certain booms in certainconfigurations, the natural frequency of the boom may range from about0.1 Hertz to about 1 Hertz (i.e., 10 seconds per cycle to 1 second percycle). For example, as the boom is moved from place to place, thestarting and stopping loads that actuate the boom may induce vibration(i.e., oscillation). Other load sources that may excite the boom includemomentum of the concrete as it is pumped along the boom, starting andstopping the pumping of concrete along the boom, wind loads that maydevelop against the boom, and/or other miscellaneous loads.

Other vehicles with booms include fire trucks in which a ladder may beincluded on the boom, fire trucks which include a boom with plumbing todeliver water to a desired location, excavators which use a boom to movea shovel, tele-handlers which use a boom to deliver materials around aconstruction site, cranes which may use a boom to move material fromplace-to-place, etc.

In certain boom applications, including those mentioned above, ahydraulic cylinder may be used to actuate the boom. By actuating thehydraulic cylinder, the boom may be deployed and retracted, as desired,to achieve a desired placement of the boom. In certain applications,counter-balance valves may be used to control actuation of the hydrauliccylinder and/or to prevent the hydraulic cylinder from uncommandedmovement (e.g., caused by a component failure).

Conventional solutions for reducing the above mentioned oscillations aretypically passive (i.e., orifices) which are tuned for one particularoperating point and often have a negative impact on efficiency. Manymachines/vehicles with extended booms employ counter-balance valves(CBVs) for safely and safety regulation reasons. These counter-balancevalves (CBVs) restrict/block the ability of the hydraulic control valveto sense and act upon pressure oscillations. In certain applications,such as concrete pump truck booms, oscillations are induced by externalsources (e.g., the pumping of the concrete) when the machine (e.g., theboom) is nominally stationary. In this case, the counter-balance valves(CBVs) are closed, and the main control valve is isolated from theoscillating pressure that is induced by the oscillations. There are anumber of conventional solutions that approach this problem, thattypically rely on joint position sensors to sense the oscillations(i.e., ripples) and prevent drift due to flow through aripple-cancelling valve. Some solutions also have parallel hydraulicsystems that allow a ripple-cancelling valve to operate while thecounter-balance valves (CBVs) are in place.

SUMMARY

One aspect of the present disclosure relates to systems and methods forreducing boom dynamics (e.g., boom bounce) of a boom while providingcounter-balance valve protection to the boom.

Another aspect of the present disclosure relates to a method ofcontrolling vibration in a boom. The method may include: providing ahydraulic actuator with a first and a second chamber; selecting eitherthe first or the second chamber as a locked chamber; selecting theopposite chamber as an active chamber; locking the locked chamber; andtransferring a vibration canceling fluid flow to the active chamber. Incertain embodiments, the method may further include detecting which ofthe first and the second chambers is a load holding chamber. The loadholding chamber may be selected as the locked chamber and preventdrifting of the hydraulic actuator. A first pressure of the firstchamber may, at least intermittently, be measured, and a second pressureof the second chamber may, at least intermittently, be measured. Theload holding chamber may be detected by comparing the first and thesecond pressures. Hydraulic fluid may be prevented from exiting thelocked chamber by a first counter-balance valve in a closedconfiguration. The vibration canceling fluid flow may be transferred tothe active chamber via a second counter-balance valve in an openconfiguration.

In certain embodiments, the method may further include providing a firstcontrol valve that is adapted to pressurize and drain the first chamberand providing a second control valve that is adapted to pressurize anddrain the second chamber. Pressurizing a pilot of the secondcounter-balance valve may be done with the first control valve andthereby configure the second counter-balance valve in the openconfiguration. Generating the vibration canceling fluid flow may be donewith the second control valve.

In certain embodiments, the method may further include measuringpressure ripples at the load holding chamber and reducing a magnitude ofthe pressure ripples by the transferring of the vibration cancelingfluid flow to the active chamber. In certain embodiments the method mayfurther include measuring first pressure ripples at the active chamberand reducing a magnitude of second pressure ripples at the load holdingchamber by the transferring of the vibration canceling fluid flow to theactive chamber. The measuring of the first pressure ripples at theactive chamber and the transferring of the vibration canceling fluidflow to the active chamber may be separated in time.

In certain embodiments the method may further include transforming ashape of the first pressure ripples into a flow command that forms thevibration canceling fluid flow by multiplying the shape of the firstpressure ripples by a gain and/or phase shifting the shape of the firstpressure ripples. The gain may be a fixed gain and/or the phase shiftingmay be constant phase shifting. The gain may be a variable gain and/orthe phase shifting may be variable phase shifting. At least one of thevariable gain and the variable phase shifting may be adjusted byfeedback. The feedback may include the second pressure ripples at theload holding chamber. The feedback may include a position of thehydraulic actuator. The feedback may include an operator input.

In certain embodiments the method may further include generating areference signal starting prior to transferring the vibration cancelingfluid flow to the active chamber, deriving a variable from acharacteristic measured from the hydraulic actuator, summing thereference signal and the variable and thereby deriving a controlvariable, and/or forming a flow characteristic of the vibrationcanceling fluid flow with the control variable. The reference signal maybe filtered with a moving average filter. The reference signal may begenerated from a first pressure measured at the first chamber and from asecond pressure measured at the second chamber. The first chamber of thehydraulic actuator may be a head chamber, and the second chamber of thehydraulic actuator may be a rod chamber. The first chamber of thehydraulic actuator may be the rod chamber, and the second chamber of thehydraulic actuator may be the head chamber. The first and secondchambers may switch between the head and rod chambers as the externalload switches direction.

A variety of additional aspects will be set forth in the descriptionthat follows These aspects can relate to individual features and tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad concepts uponwhich the embodiments disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a hydraulic system including ahydraulic cylinder with a pair of counter-balance valves and configuredwith a hydraulic cylinder control system with a pair of control valvesaccording to the principles of the present is disclosure;

FIG. 2 is the schematic illustration of FIG. 1, but with a valveblocking fluid flow to a pilot of one of the counter-balance valves ofFIG. 1;

FIG. 3 is a schematic illustration of a hydraulic cylinder suitable foruse with the hydraulic cylinder control system of FIG. 1 according tothe principles of the present disclosure;

FIG. 4 is a schematic illustration of a vehicle with a boom system thatis actuated by one or more cylinders and controlled with the hydraulicsystem of FIG. 1 according to the principles of the present disclosure;

FIG. 5 is a schematic illustration of a control system suitable for usewith the hydraulic cylinder control system of FIG. 1 according to theprinciples of the present disclosure;

FIG. 6 is a graph illustrating a simulation of the hydraulic cylindercontrol system of FIG. 1;

FIG. 7 is a schematic illustration of another control system suitablefor use with the hydraulic cylinder control system of FIG. 1 accordingto the principles of the present disclosure;

FIG. 8 is a flow chart of an example method of implementing a controlstrategy for reducing boom oscillation according to the principles ofthe present disclosure; and

FIG. 9 is a rotary actuator writable for use with the hydraulic systemof FIG. 1 according to the principles of the present disclosure.

DETAILED DESCRIPTION

According to the principles of the present disclosure, a hydraulicsystem is adapted to actuate a hydraulic cylinder 110, includingcounter-balance valves 300 and 400, and further provides means forcounteracting vibrations to which the hydraulic cylinder 110 is exposed.As illustrated at FIG. 1, an example system 600 is illustrated with thehydraulic cylinder 110 (i.e., a hydraulic actuator), the counter-balancevalve 300, and the counter-balance valve 400. The hydraulic cylinder 110and the counter-balance valves 300, 400 of FIG. 1 may be the same asthose in certain prior art systems. The hydraulic system 600 maytherefore be retrofitted to an existing and/or a conventional hydraulicis system. The depicted embodiment illustrated at FIG. 1 can represent aprior art hydraulic system retrofitted by replacing a conventionalhydraulic control valve with a valve assembly 690, described in detailbelow, and by adding valves 350 and/or 450. Certain features of thehydraulic cylinder 110 and the counter-balance valves 300, 400 may bethe same or similar between the hydraulic system 600 and certain priorart hydraulic systems.

It will be understood that certain concepts and principles disclosedherein apply to both linear and rotary actuators. The hydraulic cylinder110, illustrated in the Figures, is an example actuator. The hydrauliccylinder 110 is an example hydraulic cylinder and an example linearactuator. In certain applications, the hydraulic cylinder 110 may bereplaced with a rotary actuator 1108 (see FIG. 9). The rotary actuator1108 may operate over a range of less than 360 degrees, a range of 360degrees, a range of more than 360 degrees, or may have an unlimitedrange in one or both rotational directions.

According to the principles of the present disclosure a control strategyfor the hydraulic system 600 includes a method for using the valveassembly 690, with two independent directional control valves (DCV) 700,800, in conjunction with a mechanism for opening one of thecounter-balance valves 300 or 400 and locking the other of thecounter-balance valves 400 or 300 that is the load-holding counterbalance valve. Oscillations in a boom 30 may thereby be reduced whilealso preventing drift in the hydraulic cylinder 110 or rotary actuator1108.

In certain embodiments, the control strategy uses only pressure sensors(e.g., pressure sensors 610 ₁, 610 ₂, 620 ₁, 620 ₂). The pressuresensors (e.g., the pressure sensors 610 ₁, 610 ₂) may be included in thevalve assembly 690. A position sensor (e.g., position sensors 620 ₃) maynot be required. Thus, the hardware and sensors required may be reducedin comparison with conventional arrangements.

The control strategy may include a cross-port pressure feedback controlsystem. In particular, the hydraulic cylinder 110 or rotary actuator110R is actuated by the pair of independent metering valves 700, 800which can control the flow in and flow out of the two hydraulic cylinderchambers 116, 116R, 118, 118R, respectively. Before active vibrationcontrol is turned on, pressures in both chambers 116, 116R, 118, 118Rare recorded and are used to initialize a reference pressure to betracked. When the active vibration control is turned on, the loadholding chamber 116, 116R or 118, 118R is locked, and no flow enters orleaves the load holding chamber 116, 116R or 118, 118R via the controlvalve 700 or 800, respectively. In certain embodiments, the pressuresensor 620 ₁, 620 ₂ installed on the load holding chamber 116, 116R or118, 118R continuously measures the pressure in the load holding chamber116, 116R or 118, 118R.

After the load holding chamber 116, 1168 or 118, 118R is locked, thevibration control motions of the hydraulic cylinder 110 or rotaryactuator 110R are accomplished by manipulating the pressure in thechamber 118, 118R or 116, 116R (i.e., the active chamber) that isopposite the load holding chamber 116, 116R or 118, 118R. Positiondrifting of the hydraulic cylinder 110 or rotary actuator 110R iseffectively prevented by the locked counter-balance valve 300 or 400 onthe load-holding side.

The control objective for the non-load-holding chamber 118, 118R or 116,116R is to stabilize the pressure in the load holding chamber 116, 116Ror 118, 118R which is defined as the cross-port pressure feedbackcontrol. The cross-port pressure feedback control can be illustrated bya repetitive external load force acting as an external vibration 960applied on the hydraulic cylinder 110 or rotary actuator 110R. If bothchambers 116, 116R and 118, 118R are locked, the pressures in bothchambers 116, 116R and 118, 118R will eventually achieve repetitivepatterns, with constant mean values (see FIG. 6). The mean pressurevalues are updated in real time in a controller 640. The controlobjective is to reduce pressure ripples in the load-holding chamber 116,116R or 118, 118R by controlling the flow inflow out of thenon-load-holding chamber 118, 118R or 116, 116R. Upon the load-holdingchamber pressure being stabilized, the pressure in the non-load-holdingchamber 118, 118R or 116 116R produces enough hydraulic force tocompensate the external repetitive load force, acting as the externalvibration 960, and the cylinder position is stabilized.

According to the principles of the present disclosure, the controlstrategy may be implemented on the hydraulic system 600. The hydraulicsystem 600 is illustrated at FIG. 1. The counter-balance valve 300controls and/or transfers hydraulic fluid flow into and out of the firstchamber 116 of the hydraulic cylinder 110 of the system 600. Likewise,the second counter-balance valve 400 controls and/or transfers hydraulicfluid flow into and out of the second chamber 118 of the hydrauliccylinder 110. In particular, a port 302 of the counter-balance valve 300is connected to a port 122 of the hydraulic cylinder 110. Likewise, aport 402 of the counter-balance valve 400 is fluidly connected to a port124 of the hydraulic cylinder 110. As depicted, a fluid line 562schematically connects the port 302 to the port 122, and a fluid line564 connects the port 402 to the port 124. The counter-balance valves300, 400 are typically mounted directly to the hydraulic cylinder 110.The port 302 may directly connect to the port 122, and the port 402 maydirectly connect to the port 124.

The counter-balance valves 300, 400 provide safety protection to thesystem 600. In particular, before movement of the cylinder 110 canoccur, hydraulic pressure must be applied to both of the counter-balancevalves 300, 400. The hydraulic pressure applied to one of thecounter-balance valves 300, 400 is delivered to a corresponding one ofthe ports 122, 124 of the hydraulic cylinder 110 thereby urging a piston120 of the hydraulic cylinder 110 to move. The hydraulic pressureapplied to an opposite one of the counter-balance valves 400, 300 allowshydraulic fluid to flow out of the opposite port 124, 122 of thehydraulic cylinder 110. By requiring hydraulic pressure at thecounter-balance valve 300, 400 corresponding to the port 122, 124 thatis releasing the hydraulic fluid, a failure of a hydraulic line, avalve, a pump, etc. that supplies or receives the hydraulic fluid fromthe hydraulic cylinder 110 will not result in uncommanded movement ofthe hydraulic cylinder 110.

Turning now to FIG. 1, the system 600 will be described in detail. Asdepicted, the valve assembly 690 is used to control the hydrauliccylinder 110. The hydraulic cylinder 110 may be urged to extend bysupplying hydraulic fluid to the chamber 116, and hydraulic fluid in thechamber 118 of the hydraulic cylinder 110 is urged out of the port 124of the cylinder 110. Hydraulic fluid leaving the port 124 returns to ahydraulic tank. The hydraulic cylinder 10 may be effectively stopped bythe valve assembly 690 by shutting of hydraulic fluid flow to thechambers 116 and 118. The hydraulic cylinder 110 may be urged to retractby supplying hydraulic fluid to the chamber 118, and hydraulic fluid inthe chamber 116 of the hydraulic cylinder 110 is urged out of the port122 of the cylinder 110. Hydraulic fluid leaving the port 122 returns tothe hydraulic tank. In certain embodiments, the supply line 502 supplieshydraulic fluid at a constant or at a near constant supply pressure. Incertain embodiments, the return line 504 receives hydraulic fluid at aconstant or at a near constant return pressure. An operator and/or acontrol system may control the valve assembly 690 as desired and therebyachieve extension, retraction, and/or locking of the hydraulic cylinder110.

A function of the counter-balance valves 300, 400 when the hydrauliccylinder 110 is extending will now be discussed in detail. Uponhydraulic fluid pressurizing a port 304 of the counter-balance valve 300and a port 406 of the counter-balance valve 400. Hydraulic fluidpressure applied at the port 304 of the counter-balance valve 300 flowspast a spool 310 of the counter-balance valve 300 and past a check valve320 of the counter-balance valve 300 and thereby flows from the port 304to the port 302 through a passage 322 of the counter-balance valve 300.The hydraulic fluid pressure further flows through the port 122 and intothe chamber 116 (i.e., a meter-in chamber). Pressure applied to the port406 of the counter-balance valve 400 moves a spool 410 of thecounter-balance valve 400 against a spring 412 and thereby compressesthe spring 412. Hydraulic fluid pressure applied at the port 406 therebyopens a passage 424 between the port 402 and the port 404. By applyinghydraulic pressure at the port 406 (i.e., a pilot), hydraulic fluid mayexit the chamber 118 (i.e., a meter-out chamber) through the port 124,through the line 564, through the passage 424 of the counter-balancevalve 400 across the spool 410, through a hydraulic line 554, throughthe valve 800, and through the return line 504 into the tank. Themeter-out side may supply backpressure.

A function of the counter-balance valves 300, 400 when the hydrauliccylinder 110 is retracting will now be discussed in detail. Uponhydraulic fluid pressuring a port 404 of the counter-balance valve 400and a port 306 of the counter-balance valve 300. Hydraulic fluidpressure applied at the port 404 of the counter-balance valve 400 flowspast the spool 410 of the counter-balance valve 400 and past a checkvalve 420 of the counter-balance valve 400 and thereby flows from theport 404 to the port 402 through a passage 422 of the counter-balancevalve 400. The hydraulic fluid pressure further flows through the port124 and into the chamber 118 (i.e., a meter-in chamber). Hydraulicpressure applied to the port 306 of the counter-balance valve 300 movesthe spool 310 of the counter-balance valve 300 against a spring 312. andthereby compresses the spring 312. Hydraulic fluid pressure applied atthe port 306 thereby opens a passage 324 between the port 302 and theport 304. By applying hydraulic pressure at the port 306 (i.e., apilot), hydraulic fluid may exit the chamber 116 (i.e., a meter-outchamber) through the port 122, through the line 562, through the passage324 of the counter-balance valve 300 across the spool 310, through thehydraulic line 552, through the valve 700, and through the return line504 into the tank. The meter-out side may supply backpressure.

The hydraulic cylinder 110 may hold a net load 90 that, in general, mayurge retraction or extension of a rod 126 of the cylinder 110.Alternatively, the rotary hydraulic actuator 11 OR may hold a net loadthat, in general, may urge a first rotation or a second rotation of ashaft 126R of the rotary hydraulic actuator 110R (see FIG. 9). The rod126 is connected to the piston 120 of the cylinder 110. If the load 90urges extension of the hydraulic cylinder 110, the chamber 118 on a rodside 114 of the hydraulic cylinder 110 is pressurized by the load 90,and the counter-balance valve 400 acts to prevent the release ofhydraulic fluid from the chamber 118 and thereby acts as a safety deviceto prevent uncommanded extension of the hydraulic cylinder 110. In otherwords, the counter-balance valve 400 locks the chamber 118. In additionto providing safety, the locking of the chamber 118 prevents drifting ofthe cylinder 110. Vibration control may be provided via the hydrauliccylinder 110 by dynamically pressurizing and depressurizing the chamber116 on a head side 112 of the hydraulic cylinder 110. As the hydrauliccylinder 110, the structure to which the hydraulic cylinder 110 isattached, and the hydraulic fluid within the chamber 118 are at leastslightly deformable, selective application of hydraulic pressure to thechamber 116 will cause movement (e.g., slight movement) of the hydrauliccylinder 110. Such movement, when timed in conjunction with the controlstrategy, may be used to counteract vibrations of the system 600.

If the load 90 urges retraction of the hydraulic cylinder 110, thechamber 116 on the head side 112 of the hydraulic cylinder 110 ispressurized by the load 90, and the counter-balance valve 300 acts toprevent the release of hydraulic fluid from the chamber 116 and therebyacts as a safety device to prevent uncommanded retraction of thehydraulic cylinder 110. In other words, the counter-balance valve 300locks the chamber 116. In addition to providing safety, the locking ofthe chamber 116 prevents drifting of the cylinder 110. Vibration controlmay be provided via the hydraulic cylinder 110 by dynamicallypressurizing and depressurizing the chamber 118 on the rod side 114 ofthe hydraulic cylinder 110. As the hydraulic cylinder 110, the structureto which the hydraulic cylinder 110 is attached, and the hydraulic fluidwithin the chamber 116 are at least slightly deformable, selectiveapplication of hydraulic pressure to the chamber 118 will cause movement(e.g., slight movement) of the hydraulic cylinder 110. Such movement,when timed in conjunction with the control strategy, may be used tocounteract vibrations of the system 600.

The load 90 is depicted as attached via a rod connection 128 to the rod126 of the cylinder 110. In certain embodiments, the load 90 is atensile or a compressive load across the rod connection 128 and the headside 112 of the cylinder 110.

As is further described below, the system 600 provides a controlframework and a control mechanism to achieve boom vibration reductionfor both off-highway vehicles and on-highway vehicles. The vibrationreduction may be adapted to reduced vibrations in booms with relativelylow natural frequencies (e.g., the concrete pump truck boom). Thehydraulic system 600 may also be applied to booms with relatively highnatural frequencies (e.g., an excavator boom). Compared withconventional methods, the hydraulic system 600 may achieve vibrationreduction of booms with fewer sensors and a simplified controlstructure. The vibration reduction method may be implemented whileassuring protection from failures of certain hydraulic lines, hydraulicvalves, and/or hydraulic pumps, as described above. The protection fromfailure may be automatic and/or mechanical. In certain embodiments, theprotection from failure may not require any electrical signal and/orelectrical power to engage. The protection from failure may be and/ormeet a regulatory requirement (e.g., an ISO standard). The regulatoryrequirement may require certain mechanical means of protection that isprovided by the hydraulic system 600.

Certain booms may include stiffness and inertial properties that cantransmit and/or amplify dynamic behavior of the load 90. As the dynamicload 90 may include external force/position disturbances that areapplied to the boom, severe vibrations (i.e., oscillations) may result,especially when these disturbances are near the natural frequency of theboom. Such excitation of the boom by the load 90 may result in saferissues and/or decrease productivity and/or reliability of the boomsystem. By measuring parameters of the hydraulic system 600 andresponding appropriately, effects of the disturbances may be reducedand/or minimized or even eliminated. The response provided may beeffective over a wide variety of operating conditions. According to theprinciples of the present disclosure, vibration control may be achievedusing minimal numbers of sensors.

According to the principles of the present disclosure, hydraulic fluidflow to the chamber 116 of the head side 112 of the cylinder 110, andhydraulic fluid flow to the chamber 118 of the rod side 114 of thecylinder 110 are independently controlled and/or metered to realize boomvibration reduction and also to prevent the cylinder 110 from drifting.According to the principles of the present disclosure, the hydraulicsystem 600 may be configured similar to a conventional counter-balancesystem.

In certain embodiments, the hydraulic system 600 is configured to theconventional counter-balance configuration when a movement of thecylinder 110 is commanded. As further described below, the hydraulicsystem 600 may enable measurement of pressures within the chambers 116and/or 118 of the cylinder 110 at a remote location away from thehydraulic cylinder 110 (e.g., at sensors 610). This architecture therebymay reduce mass that would otherwise be positioned on the boom and/ormay simplify routing of hydraulic lines (e.g., hard tubing and hoses).Performance of machines such as concrete pump booms and/or lift handlersmay be improved by such simplified hydraulic line routing and/or reducedmass on the boom. In certain embodiments, the hydraulic system 600 mayenable measurement of the pressures within the chambers 116 and/or 118of the cylinder 110 at the hydraulic cylinder 110 (e.g., at sensors 620₁ and/or 620 ₂). In the embodiment depicted at FIG. 1, the sensor 620 ₁may measure the pressure within the chamber 116, and the sensor 620 ₂may measure the pressure within the chamber 118. Signals from some orall of the sensors 610, 620 may be sent to the controller 640 (e.g., foruse as feedback signals).

The counter-balance valves 300 and 400 may be components of a valvearrangement 840 (i.e., a valve set). The valve arrangement 840 mayinclude various hydraulic components that control and/or regulatehydraulic fluid flow to and/or from the hydraulic cylinder 110. Thevalve arrangement 840 may further include the control valve 700 (e.g., aproportional hydraulic valve), the control valve 800 (e.g., aproportional hydraulic valve), the valve 350 (e.g., a 2-way valve), andthe valve 450 (e.g., a 2-way valve). The control valves 700 and/or 800may be high bandwidth and/or high resolution control valves.

In the depicted embodiment of FIG. 1, a node 51 is defined at the port302 of the counter-balance valve 300 and the port 122 of the hydrauliccylinder 110; a node 52 is defined at the port 402 of thecounter-balance valve 400 and the port 124 of the hydraulic cylinder110; a node 53 is defined at the port 304 of the counter-balance valve300, a port 462. of the valve 450, and the port 702 of the hydraulicvalve 700; a node 54 is defined at the port 404 of the counter-balancevalve 400, a port 362 of the valve 350, and the port 804 of thehydraulic valve 800; a node 55 is defined at the port 306 of thecounter-balance valve 300 and a port 352 of the valve 350; and a node 56is defined at the port 406 of the counter-balance valve 400 and a port452 of the valve 450. The hydraulic valves 350 and 450 are described indetail below.

Turning now to FIG. 3, the hydraulic cylinder 110 is illustrated with vblocks 152, 154. The valve blocks 152, 154 may be separate from eachother, as illustrated, or may be a single combined valve block. Thevalve block 152 may be mounted to and/or over the port 122 of thehydraulic cylinder 110, and the valve block 154 may be mounted to and/orover the port 124 of the hydraulic cylinder 110. The valve blocks 152,154 may be directly mounted to the hydraulic cylinder 110. The valveblock 152 may include the counter-balance valve 300 and/or the valve350, and the valve block 154 may include the counter-balance valve 400and/or the valve 450. The valve blocks 152 and/or 154 may includeadditional components of the valve arrangement 840. The valve blocks152, 154, and/or the single combined valve block may include sensorsand/or sensor ports (e.g., pressure and/or flow sensors and/orcorresponding ports).

Turning now to FIG. 4, an example boom system 10 is described andillustrated in detail. The boom system 10 may include a vehicle 20 and aboom 30. The vehicle 20 may include a drive train 22 (e.g., includingwheels and/or tracks). As depicted at FIG. 5, rigid retractable supports24 are further provided on the vehicle 20. The rigid supports 24 mayinclude feet that are extended to contact the ground and thereby supportand/or stabilize the vehicle 20 by bypassing ground support away fromthe drive train 22 and/or suspension of the vehicle 20. In othervehicles (e.g., vehicles with tracks, vehicles with no suspension), thedrive train 22 may be sufficiently rigid and retractable rigid supports24 may not be needed and/or provided.

As depicted at FIG. 4, the boom 30 extends from a first end 32 to asecond end 34. As depicted, the first end 32 is rotatably attached(e.g., by a turntable) to the vehicle 20. The second end 34 may bepositioned by actuation of the boom 30 and thereby be positioned asdesired. In certain applications, it may be desired to extend the secondend 34 a substantial distance away front the vehicle 20 in a primarilyhorizontal direction. In other embodiments, it may be desired toposition the second end 34 vertically above the vehicle 20 a substantialdistance. In still other applications, the second end 34 of the boom 30may be spaced both vertically and horizontally from the vehicle 20. Incertain applications, the second end 34 of the boom 30 may be loweredinto a hole and thereby be positioned at an elevation below the vehicle20,

As depicted, the boom 30 includes a plurality of boom segments 36.Adjacent pairs of the boom segments 36 may be connected to each other bya corresponding joint 38. As depicted, a first boom segment 36 ₁ isrotatably attached to the vehicle 20 at a first joint 381. The firstboom segment 36 ₁ may be mounted by two rotatable joints. For example,the first rotatable joint may include a turntable, and the secondrotatable joint may include a horizontal axis. A second boom segment 36₂ is attached to the first boom segment 36 ₁ at a second joint 38 ₂.Likewise, a third boom segment 36 ₃ is attached to the second boomsegment 36 ₂ at a joint 38 ₃, and a fourth boom segment 36 ₄ is attachedto the third boom segment 36 ₃ at a fourth joint 38 ₄. A relativeposition/orientation between the adjacent pairs of the boom segments 36may be controlled by a corresponding hydraulic cylinder 110. Forexample, a relative position/orientation between the first boom segment36 ₁ and the vehicle 20 is controlled by a first hydraulic cylinder 110₁. The relative position/orientation between the first boom segment 36 ₁and the second boom segment 36 ₂ is controlled by a second hydrauliccylinder 110 ₂. Likewise, the relative position/orientation between thethird boom segment 36 ₃ and the second boom segment 362 may becontrolled by a third hydraulic cylinder 110 ₃, and the relativeposition/orientation between the fourth boom segment 36 ₄ and the thirdboom segment 36 ₃ may be controlled by a fourth hydraulic cylinder 110₄.

According to the principles of the present disclosure, the boom 30,including the plurality of boom segments 36 ₁₋₄, may be modeled andvibration of the boom 30 may be controlled by the controller 640. Inparticular, the controller 640 may send a signal 652 to the valve 700and a signal 654 to the valve 800. The signal 652 may include avibration component 652 v, and the signal 654 may include a vibrationcomponent 654 v. The vibration component 652 v, 654 v may cause therespective valve 700, 800 to produce a vibratory flow and/or a vibratorypressure at the respective port 702, 804. The vibratory flow arid/or thevibratory pressure may be transferred through the respectivecounter-balance valve 300, 400 and to the respective chamber 116, 118 ofthe hydraulic cylinder 110.

The signals 652, 654 of the controller 640 may also include move signalsthat cause the hydraulic cylinder 110 to extend and retract,respectively, and thereby actuate the boom 30. As will be furtherdescribed below, the signals 652, 654 of the controller 640 may alsoinclude selection signals that select one of the counter-balance valves300, 400 as a holding counter-balance valve and select the other of thecounter-balance valves 400, 300 as a vibration flow/pressuretransferring counter-balance valve. In the depicted embodiment, a loadedone of the chambers 116, 118 of the hydraulic cylinder 110, that isloaded by the net load 90, corresponds to the holding counter-balancevalve 300, 400, and an unloaded one of the chambers 118, 116 of thehydraulic cylinder 110, that is not loaded by the net load 90,corresponds to the vibration flow/pressure transferring counter-balancevalve 400, 300. In certain embodiments, the vibration component 652 v or654 v may be transmitted to the control valve 800, 700 that correspondsto the unloaded one of the chambers 118, 116 of the hydraulic cylinder110.

The controller 640 may receive input from various sensors, including thesensors 610, optional remote sensors 620, position sensors, LVDTs,vision base sensors, etc. and thereby compute the signals 652, 654,including the vibration component 652 v, 654 v and the selectionsignals. The controller 640 may include a dynamic model of the boom 30and use the dynamic model and the input from the various sensors tocalculate the signals 652, 654, including the vibration component 652 v,654 v and the selection signals. In certain embodiments, the selectionsignals include testing signals to determine the loaded one and/or theunloaded one of the chambers 116, 118 of the hydraulic cylinder 110.

In certain embodiments, a single system such as the hydraulic system 600may be used on one of the hydraulic cylinders 110 (e.g., the hydrauliccylinder 1100. In other embodiments, a plurality of the hydrauliccylinders 110 may each be actuated by a corresponding hydraulic system600. In still other embodiments, all of the hydraulic cylinders 110 mayeach be actuated by a system such as the system 600.

Turning now to FIG. 1, certain elements of the hydraulic system 600 willbe described in detail. The example hydraulic system 600 includes theproportional hydraulic control valve 700 and the proportional hydrauliccontrol valve 800. In the depicted embodiment, the hydraulic valves 700and 800 are three-way three position proportional valves. The valves 700and 800 may be combined within a common valve body. In certainembodiments, some or all of the valves 300, 350, 400, 450, 700, and/or800 of the hydraulic system 600 may be combined within a common valvebody and/or a common valve block. In certain embodiments, some or all ofthe valves 300, 350, 400, 450, 700, and/or 800 of the valve arrangement840 may be combined within a common valve body and/or a common valveblock. In certain embodiments, the valves 300, 350, and/or 700 of thevalve arrangement 840 may be combined within a common valve body and/ora common valve block. In certain embodiments, the valves 400, 450,and/or 800 of the valve arrangement 840 may be combined within a commonvalve body and/or a common valve block.

The hydraulic valve 700 may include a spool 720 with a firstconfiguration 722, a second configuration 724, and a third configuration726. As illustrated, the spool 720 is at the third configuration 726.The valve 700 includes a port 702, a port 712, and a port 714. In thefirst configuration 722, the port 714 is blocked off, and the port 702is fluidly connected to the port 712. In the second configuration 724,the ports 702, 712, 714 are all blocked off In the third configuration726, the port 702 is fluidly connected to the port 714, and the port 712is blocked off.

The hydraulic valve 800 may include a spool 820 with a firstconfiguration 822, a second configuration 824, and a third configuration826. As illustrated, the spool 820 is at the third configuration 826.The valve 800 includes a port 804, a port 812, and a port 814. In thefirst configuration 822, the port 812 is blocked off, and the port 804is fluidly connected to the port 814. In the second configuration 824,the ports 804, 812, 814 are all blocked off. In the third configuration826, the port 804 is fluidly connected to the port 812, and the port 814is blocked off.

In the depicted embodiment, a hydraulic line 562 connects the port 302of the counter-balance valve 300 with the port 122 of the hydrauliccylinder 110. Node 51 may include the hydraulic line 562. A hydraulicline 564 may connect the port 402 of the counter-balance valve 400 withthe port 124 of the hydraulic cylinder 110. Node 52 may include thehydraulic line 564. In certain embodiments, the hydraulic lines 562and/or 564 are included in valve blocks, housings, etc. and may be shortin length. A hydraulic line 552 may connect the port 304 of thecounter-balance valve 300 with the port 702. of the hydraulic valve 700and with the port 462 of the valve 450. Node 53 may include thehydraulic line 552. Likewise, a hydraulic line 554 may connect the port404 of the counter-balance valve 400 with the port 804 of the hydraulicvalve 800 and with the port 362 of the valve 350. Node 54 may includethe hydraulic line 554. A hydraulic line (unnumbered) may connect theport 306 of the counter-balance valve 300 with the port 352 of the valve350, and node 55 may include this hydraulic line. Likewise, a hydraulicline (unnumbered) may connect the port 406 of the counter-balance valve400 with the port 452 of the valve 450, and node 56 may include thishydraulic line. In other embodiments, the ports 306 and 352 may directlyconnect to each other. Likewise, the ports 406 and 452 may directlyconnect to each other.

As illustrated at FIGS. 1 and 2, the valve 350 is a two-way two positionvalve. In particular, the valve 350 includes the first port 352 and thesecond port 362. The valve 350 includes a spool 370 with a firstconfiguration 372 and a second configuration 374. In the firstconfiguration 372 (depicted at FIG. 1), the port 352 and the port 362are fluidly connected. In the second configuration 374 (depicted at FIG.2), the port 362 and the port 352 are connected with a one-way flowdevice 364 (e.g., a check valve). As depicted, the valve 350 includes asolenoid 376 and a spring 378. The solenoid 376 and the spring 378 canbe used to move the spool 370 between the first configuration 372 andthe second configuration 374. As depicted, the valve spool 370 ispositioned at the first configuration 372 when the solenoid 376 isunpowered. As depicted, the one-way flow device 364 allows flow fromnode 55 to node 54 and prevents flow from node 54 to node 55 when thevalve spool 370 is positioned at the second configuration 374 (see FIG.3).

As depicted, the valve 450 is also a two-way two position valve. Inparticular, the valve 450 includes the first port 452 and the secondport 462. The valve 450 includes a spool 470 with a first configuration472 and a second configuration 474. In the first configuration 472, theport 452 and the port 462 are fluidly connected. In the secondconfiguration 474, the port 462 and the port 452 are connected with aone-way flow device 464 (e.g., a check valve). As depicted, the valve450 includes a solenoid 476 and a spring 478. The solenoid 476 and thespring 478 can be used to move the spool 470 between the firstconfiguration 472 and the second configuration 474. As depicted, thevalve spool 470 is positioned at the first configuration 472 when thesolenoid 476 is unpowered. As depicted, the one-way flow device 464allows flow from node 56 to node 53 and prevents flow front node 53 tonode 56 when the valve spool 470 is positioned at the secondconfiguration 474.

When the valves 350 and 450 are both positioned at the firstconfigurations 372 and 472 (see FIG. 1), respectively, the hydraulicsystem 600 may function the same as or similar to a conventionalhydraulic system. The hydraulic system 600 may include a “conventional”mode that configures the valves 350 and 450 at the first configurations372, 472. The “conventional” mode may disable and/or deactivate thevibration control features of the hydraulic system 600. The“conventional” mode may be selected by a machine operator and/or may beselected automatically (e.g., by the controller 640). Manual orautomatic selection of the “conventional” mode may be implemented by thecontroller 640 (e.g., by sending electrical signals to the solenoids 376and/or 476). As depicted, a lack of power at the solenoids 376, 476corresponds with the selection of the “conventional” mode. In otherembodiments, providing power to the solenoids 376 and/or 476 correspondswith the selection of the “conventional” mode (e.g., configures thevalves 350 and/or 450 at the first configurations 372 and/or 472). Incertain embodiments, the valve spools 370 and/or 470 may be manuallypositioned (e.g., by a linkage). In certain embodiments, the valvespools 370 and/or 470 may be positioned by pilot hydraulic pressure. Incertain embodiments, the “conventional” mode may be selected whencylinder movements of the hydraulic cylinder 110 are executed (e.g.,when a position configuration change of the boom 30 is executed).

When the vibration control features of the hydraulic system 600 areexecuted, one of the valves 350 and 450 may be positioned at the secondconfiguration 372, 472. For example, as depicted at FIG. 2, the chamber116 of the hydraulic cylinder 110 is the load holding and/or driftpreventing chamber, and the vibratory flow and/or the vibratory pressureis applied to the chamber 118 of the hydraulic cylinder 110. Thevibratory flow and/or the vibratory pressure may be generated by thecontrol valve 800 in response to the signal 654 v from the controller640. A pilot opening pressure (e.g., generated by the control valve 700)may be applied to the counter-balance valve 400 thereby allowing thevibratory flow and/or the vibratory pressure generated by the controlvalve 800 to bi-directionally pass through the counter-balance valve 400to the chamber 118. The vibratory flow and/or the vibratory pressurethereby act on nodes 52 and 54 of the hydraulic system 600. With thevalve 350 at the second configuration 374, the vibratory flow and/or thevibratory pressure is blocked from reaching node 55 of the hydraulicsystem 600 by the one-way flow device 364 of the valve 350, and thecounter-balance valve 300 is not opened by the vibratory flow and/or thevibratory pressure, even if a pilot opening pressure of thecounter-balance valve 300 is exceeded at node 54.

The counter-balance valve 300 may develop/exhibit internal fluid leakageunder certain conditions and/or in certain embodiments. For example, theinternal fluid leakage may transfer hydraulic fluid from node 51 to node55 and/or may transfer hydraulic fluid from node 53 to node 55. If suchinternal fluid leakage occurs and is not allowed to drain, pressure maydevelop at node 55. If the pressure at node 55 exceeds the pilot openingpressure of the counter-balance valve 300, the spool 310 may be actuatedby the pressure at node 55, and the counter-balance valve 300 may open.However, the one-way flow device 364 of the valve 350 allows node 55 todrain to node 54. In particular, the vibratory flow and/or the vibratorypressure may be generated so that at least periodically the pressure atnode 54 is below the pilot opening pressure of the counter-balance valve300. Thus, the one-way flow device 364 of the valve 350 allows node 55to drain to node 54 when the pressure at node 54 is below the pilotopening pressure of the counter-balance valve 300, and the pressure atnode 55 may remain below the pilot opening pressure of thecounter-balance valve 300 in this configuration of the hydraulic system600.

In another example, the chamber 118 of the hydraulic cylinder 110 is theload holding and/or drift preventing chamber, and the vibratory flowand/or the vibratory pressure is applied to the chamber 116 of thehydraulic cylinder 110. The vibratory flow and/or the vibratory pressuremay be generated by the control valve 700 in response to the signal 652v from the controller 640. A pilot opening pressure (e.g., generated bythe control valve 800) may be applied to the counter-balance valve 300thereby allowing the vibratory flow and/or the vibratory pressuregenerated by the control valve 700 to bi-directionally pass through thecounter-balance valve 300 to the chamber 116. The vibratory flow and/orthe vibratory pressure thereby act on nodes 51 and 53 of the hydraulicsystem 600. With the valve 450 at the second configuration 474, thevibratory flow and/or the vibratory pressure is blocked from reachingnode 56 of the hydraulic system 600 by the one-way flow device 464 ofthe valve 450, and the counter-balance valve 400 is not opened by thevibratory flow and/or the vibratory pressure, even if a pilot openingpressure of the counter-balance valve 400 is exceeded at node 53.

The counter-balance valve 400 may develop/exhibit internal fluid leakageunder certain conditions and/or in certain embodiments. For example, theinternal fluid leakage may transfer hydraulic fluid from node 52 to node56 and/or may transfer hydraulic fluid from node 54 to node 56. If suchinternal fluid leakage occurs and is not allowed to drain, pressure maydevelop at node 56. If the pressure at node 56 exceeds the pilot openingpressure of the counter-balance valve 400, the spool 410 may be actuatedby the pressure at node 56, and the counter-balance valve 400 may open.However, the one-way flow device 464 of the valve 450 allows node 56 todrain to node 53. In particular, the vibratory flow and/or the vibratorypressure may be generated so that at least periodically the pressure atnode 53 is below the pilot opening pressure of the counter-balance valve400. Thus, the one-way flow device 464 of the valve 450 allows node 56to drain to node 53 when the pressure at node 53 is below the pilotopening pressure of the counter-balance valve 400, and the pressure atnode 56 may remain below the pilot opening pressure of thecounter-balance valve 400 in this configuration of the hydraulic system600.

In other embodiments, other methods of draining nodes 55 and/or 56 maybe implemented.

In certain applications, the hydraulic actuator (e.g., the hydrauliccylinder 110) may always be or may predominantly be loaded in a samedirection when the vibration control features (e.g., of the hydraulicsystem 600) are desired. For example, the hydraulic cylinder 110 ₁ ofthe boom 30 may always be or may predominantly be loaded in compression,and the chamber 116 of the hydraulic cylinder 110 ₁ may always be or maypredominantly be the load holding and/or drift preventing chamber whenthe vibration control features are desired. In such applications, one ofthe valves 350 Of 450 may be removed from the hydraulic system 600. Forexample, if the chamber 116 of the hydraulic cylinder 110 is always oris predominantly the load holding and/or drift preventing chamber, thevalve 450 may be removed and nodes 53 and 56 may be combined. As anotherexample, if the chamber 118 of the hydraulic cylinder 110 is always oris predominantly the load holding and/or drift preventing chamber, thevalve 350 may be removed and nodes 54 and 55 may be combined.

The valve 350 allows the vibratory flow and/or the vibratory pressuregenerated by the control valve 800 to exceed the pilot opening pressureof the counter-balance valve 300 without opening the counter-balancevalve 300. Likewise, the valve 450 allows the vibratory flow and/or thevibratory pressure generated by the control valve 700 to exceed thepilot opening pressure of the counter-balance valve 400 without openingthe counter-balance valve 400. Thus, the valves 350 and 450 allow thevibratory flow and/or the vibratory pressure to reach pressures limitedby the supply pressure, and a vibratory response force/displacement 950can be correspondingly aggressive.

In certain environments, the vibratory response force/displacement 950may be suitable at pressures below the pilot opening pressure of thecounter-balance valve 300, 400. In such or similar embodiments and/orenvironments, the valves 350, 450 may remain at the first configuration372, 472, and/or the hydraulic system 600 may be operated the same as orsimilar to a hydraulic system 600 of Patent Application Ser. No.61/872,424, filed on Aug. 30, 2013, entitled Control Method and Systemfor Using a Pair of Independent Hydraulic Metering Valves to Reduce BoomOscillations, which is hereby incorporated by reference in its entirety.

Sensors that measure temperature and/or pressure at various ports of thevalves 700, 800 and/or at other locations may be provided. Inparticular, a sensor 610 ₁ is provided adjacent the port 702 of thevalve 700. As depicted, the sensor 610 ₁ is a pressure sensor and may beused to provide dynamic information about the system 600 and/or the boomsystem 10. As depicted at FIGS. 1 and 2, a second sensor 610 ₂ isprovided adjacent the port 804 of the hydraulic valve 800. The sensor610 ₂ may be a pressure sensor and may be used to provide dynamicinformation about the hydraulic system 600 and/or the boom system 10. Asfurther depicted at FIGS. 1 and 2, a third sensor 610 ₃ may be providedadjacent the port 814 of the valve 800, and a fourth sensor 610 ₄ may beprovided adjacent the port 812 of the valve 800. The sensors 610 ₃ and610 ₄ may also be used to provide dynamic information about thehydraulic system 600 and/or the boom system 10. A sensor 620 ₁ may be apressure sensor provided adjacent the port 122 of the chamber 116 of thehydraulic cylinder 110, and a sensor 620 ₂ may be a pressure sensorprovided adjacent the port 124 of the chamber 118 of the hydrauliccylinder 110. In certain embodiments, a sensor 620 ₃ may be capable ofmeasuring relative position, velocity, and/or acceleration of the rod126 relative to the head side 112 and/or housing of the hydrauliccylinder 110. In certain embodiments, a sensor capable of measuringrelative position, velocity, and/or acceleration of the rod 126 relativeto the head side 112 and/or housing of the hydraulic cylinder 110 is notused. The sensors 620 may also be used to provide dynamic informationabout the hydraulic system 600 and/or the boom system 10. The sensors610 and 620 may provide feedback signals to the controller 640.

In certain embodiments, pressure within the supply line 502 and/orpressure within the tank line 504 are well known, and the pressuresensors 610 ₁ and 610 ₂ may be used to calculate flow rates through thevalves 700 and 800, respectively. In other embodiments, a pressuredifference across the valve 700, 800 is calculated. For example, thepressure sensor 610 ₃ and the pressure sensor 610 ₂ may be used when thespool 820 of the valve 800 is at the first position 822 and therebycalculate flow through the valve 800. Likewise, a pressure differencemay be calculated between the sensor 610 ₂ and the sensor 610 ₄ when thespool 820 of the valve 800 is at the third configuration 826. Thecontroller 640 may use these pressures and pressure differences ascontrol inputs.

Temperature sensors may further be provided at and around the valves700, 800 and thereby refine the flow measurements by allowingcalculation of the viscosity and/or density of the hydraulic fluidflowing through the valves 700, 800. The controller 640 may use thesetemperatures as control inputs.

Although depicted with the first sensor 610 ₁, the second sensor 610 ₂,the third Sensor 610 ₃, and the fourth sensor 610 ₄, fewer sensors ormore sensors than those illustrated may be used in alternativeembodiments. Further, such sensors may be positioned at various otherlocations in other embodiments. In certain embodiments, the sensors 610may be positioned within a common valve body. In certain embodiments, anUltronics® servo valve available from Eaton Corporation may be used. TheUltronics® servo valve provides a compact and high performance valvepackage that includes two three-way valves (i.e., the valves 700 and800), the pressure sensors 610, and a pressure regulation controller(e.g., included in the controller 640). The Ultronics® servo valve mayserve as the valve assembly 690. The Eaton Ultronics® servo valvefurther includes linear variable differential transformers (LVDT) thatmonitor positions of the spools 720, 820, respectively. By using the twothree-way proportional valves 700, 800, the pressures of the chambers116 and 118 may be independently controlled. In addition, the flow ratesinto and/or out of the chambers 116 and 118 may be independentlycontrolled. In other embodiments, the pressure of one of the chambers116, 118 may be independently controlled with respect to a flow rateinto and/or out of the opposite chambers 116, 118.

In comparison with using a single four-way proportional valve, theconfiguration of the hydraulic system 600 can achieve and accommodatemore flexible control strategies with less energy consumption. Forexample, when the cylinder 110 is moving, the valve 700, 800 connectedwith the metered-out chamber 116, 118 can manipulate the chamberpressure while the valves 800, 700 connected with the metered-in chambercan regulate the flow entering the chamber 118, 116. As the metered-outchamber pressure is not coupled with the metered-in chamber flow, themetered-out chamber pressure can be regulated to be low and therebyreduce associated throttling losses.

The supply line 502, the return line 504, the hydraulic line 552, thehydraulic line 554, the hydraulic line 562, the hydraulic line 564, ahydraulic line extending between the ports 306 and 352, and/or ahydraulic line extending between the ports 406 and 452 may belong to aline set 550.

Upon vibration control being deactivated (e.g., by an operator input),the hydraulic system 600 may configure the valve arrangement 840 as aconventional counter-balance/control valve arrangement. The conventionalcounter-balance/control valve arrangement may be engaged when moving theboom 30 under move commands to the control valves 700, 800.

Upon vibration control being activated by an operator input), the valvearrangement 840 may effectively lock the hydraulic cylinder 110 frommoving. In particular, the activated configuration of the valvearrangement 840 may lock one of the chambers 116, 118 of the hydrauliccylinder 110 while sending vibratory pressure and/or flow to an oppositeone of the chambers 118, 116. The vibratory pressure and/or flow may beused to counteract external vibrations 960 encountered by the boom 30.

Turning again to FIGS. 1 and 2, certain components of thecounter-balance valve 300, 400 will be described in detail. Thecounter-balance valve 300, 400 includes a first port 302, 402, a secondport 304, 404, and a third port 306, 406, respectively. As depicted, theport 302, 402 is fluidly connected to a hydraulic component (e.g., thehydraulic cylinder 110). The port 304, 404 is fluidly connected to acontrol valve (e.g., the control valve 700, 800). The port 306, 406 is apilot port that is selectively fluidly connected to the port 404, 304 ofan opposite counter-balance valve via the valve 350, 450. By selectivelyconnecting the port 306, 406 to the port 404, 304 of the oppositecounter-balance valve, the port 306, 406 is also selectively fluidlyconnected to a control valve 800, 700 that is opposite the control valve700, 800 that is connected to the port 304, 404.

The spool 310, 410 is movable within a bore of the counter-balance valve300, 400. In particular, a net force on the spool 310, 410 moves orurges the spool 310, 410 to move within the bore. The spool 310, 410includes a spring area and an opposite pilot area. The spring area isoperated on by a pressure at the port 304, 404. Likewise, the pilot areais operated on by a pressure at the port 306, 406. In certainembodiments, a pressure at the port 302, 402 may have negligible orminor effects on applying a force that urges movement on the spool 310,410. In other embodiments, the spool 310, 410 may further includefeatures that adapt the counter-balance valve 300, 400 to provide arelief valve function responsive to a pressure at the port 302, 402. Inaddition to forces generated by fluid pressure acting on the spring andpilot areas, the spool 310, 410 is further operated on by a springforce. In the absence of pressure at the ports 304, 404 and 306, 406,the spring force urges the spool 310, 410 to seat and thereby preventfluid flow between the ports 302, 402 and 304, 404. As illustrated atFIG. 1, a passage 322, 422 and check valves 320, 420 allow fluid to flowfrom the port 304, 404 to the port 302, 402 by bypassing the seatedspool 310, 410. However, flow from the port 302, 402 to the port 304,404 is prevented by the check valve 320, 420, when the spool 310, 410 isseated.

A net load direction on the hydraulic cylinder 110 can be determined bycomparing the pressure measured by the sensor 620 ₁ multiplied by theeffective area of the chamber 116 and comparing with the pressuremeasured by the sensor 620 ₂ multiplied by the effective area of thechamber 118.

If the net load 90 is supported by the chamber 116, the control valve700 may supply the pilot opening pressure to the port 406 via the valve450, and the control valve 800 may supply a vibration canceling fluidflow to the chamber 118. The sensors 610 ₁ and/or 610 ₂ can be used todetect the frequency, phase, and/or amplitude of any externalvibrational inputs to the hydraulic cylinder 110. Alternatively oradditionally, vibrational inputs to the hydraulic cylinder 110 may bemeasured by an upstream pressure sensor (e.g., the sensors 620 ₁ and/or620 ₂), an external position sensor (e.g., the sensors 620 ₃), anexternal acceleration sensor (e.g., the sensors 620 ₃), and/or variousother sensors. If the net load 90 is supported by the chamber 118, thecontrol valve 800 may supply a pilot opening pressure to the port 306via the valve 350, and the control valve 700 may supply a vibrationcanceling fluid flow to the chamber 116. The sensors 610 ₁ and/or 610 ₂can be used to detect the frequency, phase, and/or amplitude of anyexternal vibrational inputs to the hydraulic cylinder 110. Alternativelyor additionally, vibrational inputs to the hydraulic cylinder 110 may bemeasured by an upstream pressure sensor (e.g., the sensors 620 ₁ and/or620 ₂), an external position sensor (e.g., the sensors 620 ₃), anexternal acceleration sensor (e.g., the sensors 620 ₃), and/or variousother sensors.

The vibration cancellation algorithm can take different forms. Incertain embodiments, the frequency and phase of the external vibrationmay 960 be identified by a filtering algorithm (e.g., by Least MeanSquares, Fast Fourier Transform, etc.). In certain embodiments, thefrequency, the amplitude, and/or the phase of the external vibration maybe identified by various conventional means. In certain embodiments,upon identifying the frequency, the amplitude, and/or the phase of theexternal vibration, a pressure signal with the same frequency andappropriate phase shift may be applied at the unloaded chamber 116, 118to cancel out the disturbance caused by the external vibration 960. Thecontrol valves 700 and/or 800 may be used along with the controller 640to continuously monitor flow through the control valves 700 and/or 800to ensure no unexpected movements occur.

In the depicted embodiments, the sensors 610 ₁ and 610 ₂ are shieldedfrom measuring the pressures at the ports 122 and 124 of the hydrauliccylinder 110, respectively, by the counter-balance valves 300 and 400.Therefore, methods independent of the sensors 610 ₁ and 610 ₂ can beused to determine the direction of the net load 90 on the cylinder 110and to determine external vibrations acting on the cylinder 110. Incertain embodiments, pressure sensors (e.g., the pressure sensors 620 ₁and 620 ₂) at the ports 122 and/or 124 may be used. In otherembodiments, the pressure sensors 610 ₁ and 610 ₂ may be used.Alternatively or additionally, other sensors such as accelerometers,position sensors, visual tracking of the boom 30, etc, may be used(e.g., a position, velocity, and/or acceleration sensor 610 ₃ thattracks movement of the rod 126 of the hydraulic cylinder 110).

A flow chart 1000 of an example method of implementing the controlstrategy for reducing boom oscillation, according to the principles ofthe present disclosure, is given at FIG. 8. The boom bounce reductioncontrol is initiated at step 1002. Step 1004 follows step 1002 anddetermines which of the chambers 116 or 118 is the load holding chamber.Step 1006 follows step 1004 and locks (e.g., removes pilot pressurefrom) the counter-balance valve (CBV) 300 or 400 corresponding to theload holding chamber. Step 1008 follows step 1006 and opens (e.g.,applies pilot pressure to) the counter-balance valve (CBV) 400 or 300corresponding to the chamber 116 or 118 opposite the load holdingchamber (i.e., the active chamber). Step 1010 follows step 1008 andmeasures the pressure within the load holding chamber to initialize areference signal. Step 1012 follows step 1010 and generates a controlsignal 652 or 654 to the valve 700 or 800 corresponding to the activechamber. In certain embodiments, the control signal 652 or 654 is basedon the measurement of the load holding pressure and the referencesignal. Step 1014 follows step 1012 and adjusts the control signal basedon the measurement of the active chamber pressure. In step 1014, aspecified average level for the pressure in the active chamber ismaintained. By maintaining the specified average level, the controlpressure is allowed to vary in both directions from the mean. Step 1016follows step 1014 but may occur continuously. Step 1016 updates thereference signal. Decision point 1018 follows step 1016 and inquireswhether boom bounce reduction is still enabled. If the result ofdecision point 1018 is “yes”, then control is transferred to step 1012.If the result of decision point 1018 is “no”, then control istransferred to an end 1020 of the flow chart 1000.

The valve arrangement 840 may be configured to apply an anti-vibration(i.e., a vibration cancelling) response as follows. If the net load 90is determined to be held by the chamber 116, the control valve 700pressurizes node 53 thereby opening the counter-balance valve 400 andfurther urging the counter-balance valve 300 to close. Upon thecounter-balance valve 400 being opened, the control valve 800 may applyan anti-vibration fluid pressure/flow to the chamber 118. The controller640 may position the valve 350 to the second configuration 374 (see FIG.2) to preclude opening the counter-balance valve 300. If the net load 90is determined to be held by the chamber 118, the control valve 800pressurizes node 54 thereby opening the counter-balance valve 300 andfurther urging the counter-balance valve 400 to close. Upon thecounter-balance valve 300 being opened, the control valve 700 may applyan anti-vibration fluid pressure/flow to the chamber 116. The controller640 may position the valve 450 to the second configuration 474 topreclude opening the counter-balance valve 400.

In embodiments where the direction of the net cylinder load 90 isindependently known to be acting on the chamber 116 but at least some ofthe parameters of the external vibration acting on the hydrauliccylinder 110 are unknown from external sensor information, the pressuresensor 610 ₂ may be used to measure pressure fluctuations within thechamber 118 and thereby determine characteristics of the externalvibration. If the direction of the net cylinder load is independentlyknown to be acting on the chamber 118 but at least some of theparameters of the external vibration acting on the hydraulic cylinder110 are unknown from external sensor information, the pressure sensor610 ₁ may be used to measure pressure fluctuations within the chamber116 and thereby determine characteristics of the external vibration.

As schematically illustrated at FIG. 1, an environmental vibration load960 is imposed as a component of the net load 90 on the hydrauliccylinder 110. As depicted at FIG. 1, the vibration load component 960does not include a steady state load component. In certain applications,the vibration load 960 includes dynamic loads such as wind loads,momentum loads of material that may be moved along the boom 30, inertialloads from moving the vehicle 20, and/or other dynamic loads. The steadystate load may include gravity loads that may vary depending on theconfiguration of the boom 30. The vibration load 960 may be sensed andestimated/measured by the various sensors 610, 620 and/or other sensors.The controller 640 may process these inputs and use a model of thedynamic behavior of the boom system 10 and thereby calculate andtransmit an appropriate vibration signal 652 v, 654 v. The signal 652 v,654 v is transformed into hydraulic pressure and/or hydraulic flow atthe corresponding valve 700, 800. The vibratory pressure/flow istransferred through the corresponding counter-balance valve 300, 400 andto the corresponding chamber 116, 118 of the hydraulic cylinder 110. Thehydraulic cylinder 110 transforms the vibratory pressure and/or thevibratory flow into the vibratory response force/displacement 950. Whenthe vibratory response 950 and the vibration load 960 are superimposedon the boom 30, a resultant vibration 970 is produced. The resultantvibration 970 may be substantially less than a vibration of the boom 30generated without the vibratory response 950. Vibration of the boom 30may thereby be controlled and/or reduced enhancing the performance,durability, safety, usability, etc. of the boom system 10. The vibratoryresponse 950 of the hydraulic cylinder 110 is depicted at FIG. 2 as adynamic component of the output of the hydraulic cylinder 110. Thehydraulic cylinder 110 may also include a steady state component (i.e.,a static component) that may reflect static loads such as gravity.

According to the principles of the present disclosure, a control methoduses independent metering main control valves 700, 800 with embeddedsensors 610 (e.g., embedded pressure sensors) that can sense oscillatingpressure and provide a ripple cancelling pressure with counter-balancevalves 300, 400 (CBVs) installed. The approach calls for locking oneside (e.g., one chamber 116 or 118) of the actuator 110 in place toprevent drifting of the actuator 110. According to the principles of thepresent disclosure, active ripple cancelling is provided, an efficiencypenalty of orifices is avoided, and/or the main control valves 700, 800may be the only control elements. According to the principles of thepresent disclosure, embedded pressure sensors 610 embedded in the valve700, 800 and/or external pressure/acceleration/position sensors 620 maybe used.

Turning now to FIG. 5, certain aspects of certain embodiments of thecontrol strategy are illustrated according to the principles of thepresent disclosure. As illustrated, in certain embodiments, no positionsensors are used to monitor a position of the rod 126 of the hydrauliccylinder 110. Furthermore, no angle sensor to show geometric informationof the boom 30 is used. The control strategy may be achieved using onlypressure sensors. In certain embodiments, two pressure sensors 620 ₁,620 ₂ are installed with one measuring each chamber 116, 118.Alternatively, one shuttle pressure sensor may be used, and only theload holding chamber pressure is sensed. FIG. 5 illustrates a “lockingmechanism” activated at chamber 116 thereby locking chamber 116 (i.e.,flow into or out of the chamber 116 is zero).

FIG. 5 illustrates cross port control. In particular, the flow feedingthe unlocked cylinder chamber 118 (i.e., the active chamber) iscontrolled based on pressure measured at the locked chamber 116. Thecontrol objective is to stabilize the pressure of the locked,load-holding chamber 116. In certain embodiments, the reference signalPref is generated by self-learning. The reference signal Pref may beinitialized by the pressure before vibration control is turned on. Oncethe vibration control is engaged, the pressure Pload of the load-holdingchamber 116 is filtered to generate Pref. A low-pass filter may be used.In certain embodiments, pressure measured at the active chamber 118 maybe used as an input of the controller 640.

Turning now to FIG. 6, a graph showing simulation results of the controlstrategy illustrates the relationships of a position of the cylinder rod126, a pressure Phead of the load holding chamber (the upper pressuretrace), a pressure Prod of the active chamber (the lower pressuretrace), and flow into the active chamber in the time domain. In thissimulation, the head chamber 116 of the cylinder 110 is the load holdingchamber. The active vibration control is turned on at t=3 seconds. Att=3 seconds, control flow is provided to the rod side cylinder chamber118. As illustrated, a size of the head side pressure ripple is reduced,while a size of the rod side pressure ripple is amplified. A cylinderposition ripple is correspondingly reduced, and a mean position of thecylinder rod 126 does not drift.

Turning now to FIG. 7, certain aspects of certain embodiments of thecontrol strategy are illustrated according to the principles of thepresent disclosure. The control strategy can provide flexibility in thetype of feedback sensor used. The frequency and/or shape of the pressureripple on the load holding side (illustrated as chamber 116) can beestimated by observing; the pressure on the non-load-holding side(illustrated as chamber 118) which may have an open counter-balancevalve and thus may be measured by the sensor 610 ₂ built in to the valve800. The shape of the disturbance 642 can then be multiplied by a gain646, phase shifted by a phase shift 648, and applied as a flow command654 v to the valve 800 of the non-load-holding chamber 118. If noadditional sensors are available, the gain 646 and/or the offset 648could be fixed values. however, this would not be robust to changes inoperating conditions. Other available measurements 644 that sense thequality of the ripple reduction (e.g., pressure sensor data, positionsensor data, operator feedback, etc.) could be used to adjust the gain646 and/or the phase shift 648.

Disturbance estimation may be used additionally or alternatively. Thepressure measured on the non-load holding side (e.g., by the pressuresensor 610 ₁, 610 ₂ built into the valve 700, 800) can be used.Repetitive control may be used to generate an estimate of thedisturbance 642. A gain 646 and/or a phase shift 648 may be applied tothe disturbance 642 to cancel the disturbance force 960. The gain 646and/or the offset 648 could be constants (i.e., open loop) requiring noadditional sensors.

Alternately, some method of feedback may be used to measure thedisturbance rejection and then adapt the gain 646 and/or the phase shift648 to improve the performance. The feedback can be any means of judgingquality of disturbance rejection (e.g., pressure on the loaded chamber,position feedback of the cylinder rod 126, operator input, etc.). Themethod illustrated at FIG. 7 gives flexibility as to the type offeedback used and allows the possibility of an open-loop (no sensor)implementation.

This application relates to U.S. Provisional Patent Applications Ser.No. 61/829,796, filed on May 31, 2013, entitled Hydraulic System andMethod for Reducing Boom Bounce with Counter-Balance Protection, andSer. No. 61/872,424, filed on Aug. 30, 2013, entitled Control Method andSystem for Using a Pair of Independent Hydraulic Metering Valves toReduce Boom Oscillations, which are hereby incorporated by reference intheir entireties.

Various modifications and alterations of this disclosure will becomeapparent to those skilled in the art without departing from the scopeand spirit of this disclosure, and it should be understood that thescope of this disclosure is not to be unduly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A method of controlling vibration in a boom, themethod comprising: providing a hydraulic actuator including a firstchamber and a second chamber; selecting one of the first and the secondchambers as a locked chamber; selecting another of the first and thesecond chambers as an active chamber; locking the locked chamber;transferring a vibration canceling fluid flow to the active chamber; andpreventing hydraulic fluid from exiting the locked chamber with a firstcounter-balance valve in a closed configuration; wherein the vibrationcanceling fluid flow is transferred to the active chamber via a secondcounter-balance valve in an open configuration.
 2. The method of claim1, further comprising: detecting which of the first and the secondchambers is a load holding chamber; wherein the load holding chamber isselected as the locked chamber; and wherein the locked chamber preventsdrifting of the hydraulic actuator.
 3. The method of claim 2, furthercomprising: at least intermittently measuring a first pressure of thefirst chamber; and at least intermittently measuring a second pressureof the second chamber; wherein the load holding chamber is detected bycomparing the first and the second pressures.
 4. The method of claim 3,further comprising: providing a first pressure sensor at leastintermittently fluidly connected to the first chamber; and providing asecond pressure sensor at least intermittently fluidly connected to thesecond chamber; wherein the first pressure sensor measures the firstpressure; and wherein the second pressure sensor measures the secondpressure.
 5. The method of claim 4, wherein the first pressure sensor iscontinuously fluidly connected to the first chamber and the secondpressure sensor is continuously fluidly connected to the second chamber.6. The method of claim 4, wherein the first pressure sensor is at leastintermittently fluidly connected to the first chamber via the firstcounter-balance valve and wherein the second pressure sensor is at leastintermittently fluidly connected to the second chamber via the secondcounter-balance valve.
 7. The method of claim 3, further comprising:providing a pressure sensor intermittently fluidly connected to thefirst chamber and intermittently fluidly connected to the secondchamber, the pressure sensor intermittently measuring the first pressureand intermittently measuring the second pressure.
 8. The method of claim2, further comprising: measuring pressure ripples at the load holdingchamber; and reducing a magnitude of the pressure ripples by thetransferring of the vibration canceling fluid flow to the activechamber.
 9. The method of claim 2, further comprising: measuring firstpressure ripples at the active chamber; and reducing a magnitude ofsecond pressure ripples at the load holding chamber by the transferringof the vibration canceling fluid flow to the active chamber.
 10. Themethod of claim 9, wherein the first pressure ripples at the activechamber are measured by a pressure sensor at a control valve adapted topressurize and drain the active chamber, wherein a counter-balance valveis positioned between the control valve and the active chamber, andwherein the counter-balance valve is open when the first pressureripples at the active chamber are measured by the pressure sensor at thecontrol valve.
 11. The method of claim 9, wherein the measuring of thefirst pressure ripples at the active chamber and the transferring of thevibration canceling fluid flow to the active chamber are separated bytime.
 12. The method of claim 9, further comprising: transforming ashape of the first pressure ripples into a flow command that forms thevibration canceling fluid flow by: multiplying the shape of the firstpressure ripples by a gain; and phase shifting the shape of the firstpressure ripples.
 13. The method of claim 12, wherein the gain is afixed gain and wherein the phase shifting is constant phase shifting.14. The method of claim 12, wherein the gain is a variable gain, whereinthe phase shifting is variable phase shifting, and wherein at least oneof the variable gain and the variable phase shifting is adjusted byfeedback.
 15. The method of claim 14, wherein the feedback is the secondpressure ripples at the load holding chamber.
 16. The method of claim14, wherein the feedback is a position of the hydraulic actuator. 17.The method of claim 14, wherein the feedback is an operator input. 18.The method of claim 2, further comprising: generating a reference signalstarting prior to transferring the vibration canceling fluid flow to theactive chamber; deriving a variable from a characteristic measured fromthe hydraulic actuator; summing the reference signal and the variableand thereby deriving a control variable; and forming a flowcharacteristic of the vibration canceling fluid flow with the controlvariable.
 19. The method of claim 18, wherein the variable at least inpart is derived from a pressure measured at the load holding chamber.20. The method of claim 18, further comprising: filtering the referencesignal with a moving average filter; wherein the reference signal isgenerated from a first pressure measured at the first chamber and from asecond pressure measured at the second chamber.
 21. The method of claim1, further comprising: providing a first control valve adapted topressurize and drain the first chamber; providing a second control valveadapted to pressurize and drain the second chamber; pressurizing a pilotof the second counter-balance valve with the first control valve andthereby configuring the second counter-balance valve in the openconfiguration; and generating the vibration canceling fluid flow withthe second control valve.
 22. The method of claim 21, furthercomprising: providing a first pressure sensor within a housing of thefirst control valve and thereby at least intermittently measuring afirst pressure of the first chamber; and providing a second pressuresensor within a housing of the second control valve and thereby at leastintermittently measuring a second pressure of the second chamber. 23.The method of claim 1, wherein the first chamber of the hydraulicactuator is a head chamber and the second chamber of the hydraulicactuator is a rod chamber.
 24. The method of claim 1, wherein the firstchamber of the hydraulic actuator is a rod chamber and the secondchamber of the hydraulic actuator is a head chamber.